芨芨台分量式钻孔应变资料可靠性分析

通过观测资料的连续率、潮汐因子内精度、自洽性检验、相对实地标定以及主要干扰因素分析,对芨芨台分量式钻孔应变观测系统的一致性和可靠性进行了评价。结果显示：(1)观测资料连续率高,精度达到了形变I类台的标准,但观测数据的自洽性检验结果相对较差,且不适宜进行相对实地标定。(2)温度和水位是主要的干扰因素,且水位在6—9月的急剧波动易导致数据失恰。     

库尔勒地震台四分量钻孔应变观测资料可靠性论证

对库尔勒地震台的巴伦台、库米什、小泉沟子台3套四分量钻孔应变仪观测数据进行多角度可靠性分析,除按常规由4个元件的读数计算2个面应变数值及相关系数值（数据自检）外,做以下补充：对潮汐因子内精度进行计算;通过相对标定元件格值,视矫正幅度大小及对数据自检效果进行改进;与同一时段相邻区域陆态网络形变观测资料进行对比,进一步论证观测资料的可靠性。结果表明,3个子台的应变观测数据可靠,能够真实反映所处区域的构造活动和应变,可以用于区域地震预测和地震科学研究。     

高台地震台钻孔应变观测资料的分析

对高台地震台2008—2012年的YRY-4分量钻孔应变观测资料进行处理与分析,结果显示:高台台YRY-4分量钻孔应变仪运行良好,产出的观测数据连续、稳定、可靠;各个分量应变潮汐因子及相位变化相对稳定,相对误差较小,符合地壳形变观测技术规范要求;各个分量应变观测数据具有明显的周期特性和同向漂移变化。     

体应变观测数据稳定性影响因素

从钻孔体应变仪器安装和标定维护、数据曲线形态及观测精度,对比分析山东省东平、邹城和陵阳地震台体应变观测资料,结果发现：东平地震台观测质量较好,质量最佳月份精度达到0.006 5;陵阳地震台无明显干扰源,精度可达0.01。因钻孔条件不同导致观测精度受到不同程度影响,如：陵阳地震台为节理裂隙较发育的安山岩,相对东平、邹城地震台较完整的花岗岩基精度稍低。     

2017年琉球群岛6级地震前佘山地震台应变观测异常

2017年5月9日琉球群岛6级地震发生前,佘山地震基准台YRY-4型钻孔应变仪的2个观测分量S₂、S₄,在M₂波潮汐因子分析中表现出明显的趋势异常。通过实地调查排除环境、气象干扰,对应变与气压观测曲线的M₂波潮汐因子γ值进行对比及量化分析,认为应变分量观测异常非环境干扰造成,应与琉球群岛6级地震发生有关。     

昭通地震中心站YRY-4钻孔应变仪观测数据干扰分析

利用YRY-4型钻孔应变仪观测资料进行自洽检验,以验证其工作稳定性;分析YRY-4型钻孔应变仪受环境干扰、场地干扰的原因及特点。结果表明,YRY-4型钻孔应变仪观测数据连续可靠;受降雨、融雪、施工等干扰影响较大,降雨后观测曲线常发生趋势性转折,且降雨的影响具有滞后性,场地施工干扰特征明显。     

山西忻州地区YRY-4分量钻孔应变仪典型干扰因素分析

YRY-4分量钻孔应变仪具有高分辨力特点,在实际运行过程中能够记录到多种类型的外界干扰,表现为观测曲线突变或趋势异常。选取山西忻州地区5套四分量钻孔应变仪自运行以来的观测资料,基于各类干扰因素特征进行分析,结果表明：在日常运行中,影响钻孔应变观测的典型干扰因素主要有观测系统、自然环境、场地环境、人为干扰等;观测系统运行稳定,映震效能良好。     

青海钻孔应变强震前异常特征分析

选取2007年以来青海省6套YRY-4分量钻孔应变仪观测资料,采用非潮汐和潮汐分析方法,对观测资料进行分析处理。结果发现:1格尔木地震台钻孔应变差应变曲线显示中短期速率异常,而德令哈地震台则显示超2倍标准差异常;2乐都地震台钻孔应变振幅因子显示突跳型异常,且异常时间短,而潮汐因子表现为下降—恢复型异常。     

钻孔应变观测干扰及异常分析

怀来台体积式钻孔应变仪安装于1988年,以应变固体潮为主要观测目标.多年来,取得了连续完整高质量的观测资料.本文列举了怀来钻孔应变的台址背景及仪器观测条件;分析了实际观测中钻孔应变资料受仪器零漂、气压、水位、降雨等因素的干扰;研究了钻孔应变在本区及邻区震前出现的记录曲线畸变、潮汐因子异常、应变固体潮畸变等不同形式的异常变化并对其进行特征分析.研究表明,钻孔应变观测是获取构造活动异常变化信息,进行地球物理研究、地震预测预报的有效途径.     

四川四分量钻孔应变观测数据精度评价

利用邱泽华等给出的观测数据和回归分析方法,计算钻孔应变仪四分量元件的相对标定系数,并根据偏差计算自检内精度等指标,对观测数据进行质量评价。选取2017年四川四分量钻孔应变观测台网记录资料,结合四分量钻孔应变仪观测特点,计算并分析应变观测仪相对标定自检内精度,客观评价观测数据精度,结果发现,2017年仁和台四分量钻孔应变数据各月及全年相对标定系数K_i最大,偏差s最小,自检内精度数值最小,表明该台钻孔应变观测数据精度最高。分析认为,相对标定自检内精度可如实反映台站记录资料的可信度,可以更好、更客观地评价台站四分量钻孔应变观测资料质量。     

降雨变化对昭通中心站YRY-4钻孔应变仪的影响分析

利用昭通中心站YRY-4钻孔应变仪前兆观测数据资料,提取降雨对该仪器观测数据的干扰事件,采用降雨总量、瞬间最大值降雨量两类降雨分类统计方法,定量分析降雨对观测数据产生的影响。结果表明:当降雨总量达到40 mm、瞬间最大值降雨量大于0.4 mm时,YRY-4钻孔应变仪观测数据受降雨干扰明显;当降雨总量大于40 mm时,降雨总量与观测数据应变量呈线性关系,瞬间最大值降雨量与降雨总量之间无显著的对应关系。分析认为,降雨干扰影响主要来自降雨渗透和台站周边地质抗水体荷载量大小两个方面。定量分析降雨干扰,有利于区分异常与干扰,积累经验,以便于及时对有效异常进行判定,为地震研究服务。      

江宁地震台YRY-4型四分量钻孔应变仪可靠性检验

江宁地震台YRY-4型四分量钻孔应变仪于2006年12月安装运行,多年来积累了大量应变观测数据。采用Venedikov调和及相对标定等方法,从观测数据年变幅度、连续率及稳定性等方面,检验该台钻孔应变可靠性,结果表明,2009年以来,江宁地震台分量钻孔应变观测变仪器运行稳定、可靠,观测资料连续,符合地壳形变观测技术规范要求。     

徐州地震台2016年11月—2017年YRY-4分量钻孔应变仪异常核实

2016年11月-2017年,徐州地震台YRY-4分量钻孔应变曲线出现"漏斗"状向下凹陷的压性变化,从场地环境、观测环境、观测系统进行现场核实,并对异常期间的观测数据进行对比分析,排除外界干扰及仪器自身问题,认为此次数据畸变可能反映了地下应力的真实变化,应为地下地质构造发生变化所致。     

INFLUENCE OF PUMPING ON FOUR-COMPONENT BOREHOLE STRAIN AT TAI'AN SEISMIC STATION AND ITS INTERFERENCE MECHANISM

Four-component borehole strainmeter (FCBS) is one kind of high-precision borehole strain observation instruments invented in China. As a kind of near-surface deformation observation instrument, FCBS is also easily disturbed by the external environment factors. As a common factor, pumping has significant influence on FCBS observation. Existing studies mostly identify the pumping interference from the perspective of observation curve morphology, relatively few studies focus on its interference mechanism. In order to truly capture earthquake precursor information, it is necessary to study the interference mechanism. In recent years, RZB-3 type FCBS at Tai'an seismic station has been seriously affected by pumping, so it is necessary and also feasible to study the interference mechanism of pumping. Since the influence of pumping interference on borehole strainmeter is common, this work would be very practical and be used for reference by other borehole strain observation stations. We find that the original observation curves and observed surface strain, shear strain from RZB-3 type FCBS at Tai'an seismic station have the characteristics of synchronous change with the borehole water level, in which the linear correlation coefficient between the two observed shear strain curves and borehole water level reached 0.70 and 0.82 respectively. We further find that the principal strain direction of borehole and borehole water level after normalization meet the nonlinear function as y=1.217arctan(x)^0.224-0.284. The above phenomenon indicates that the observation of RZB-3 type FCBS at Tai'an seismic station is significantly affected by the borehole water level, and the influence is more obvious and the gradient is larger at the stage of low water level. Pumping interference often appears in low water level stage and changes the rock pore pressure state. Statistics show that pumping interference affects the borehole strain state. To investigate the interference mechanism of pumping to RZB-3 type FCBS at Tai'an seismic station, we take a known pumping as an example, in which we study the principal strain state of the borehole in three periods of normal pumping, interruption of pumping and resuming pumping respectively. During each period, we solve 3 parameters of the principal plane strain state, i.e. the maximum principal strain rate, the minimum principal strain rate and the maximum principal strain direction from four observation equations of FCBS by nonlinear iterative least squares algorithm. On the other hand, concentrated load model (CLM) is used to simulate the mechanical mechanism of pumping. Firstly, the depth of FCBS relative to pumping source and the concentrated load at pumping source are inversed, then, the strain state surrounding the pumping well, including the state at RZB-3 borehole, is simulated by forward modeling. By comparing these results, we find that: (1)The concentrated load at pumping source inversed by CLM during periods of normal pumping and resuming pumping are both located at or near the bottom of the pumping well, which is consistent with the actual situation, indicating that mechanism and degree of the influence of pumping on borehole strain are well simulated by CLM. (2)The observed strain state is consistent with the simulation result of pumping interference by forward modeling, indicating that the principal strain state of borehole calculated based on observation of FCBS reflects the true strain state of borehole under different pumping states.(3)The inversed concentrated load at pumping source during pumping periods is significant greater than the load of the pumped water, indicating that the pumping process has more significant influence on the pore pressure of rocks than the load of the pumped water. Even though CLM is an approximate simulation since it's based on some elastic assumptions, the interference mechanism of pumping on RZB-3 type FCBS at Tai'an seismic station is well explained, which is maybe very helpful for studying the influence of pumping interference on other deformation instruments, locating the unknown pumping source and studying the characteristics of pore pressure of rocks.     

泰安台YRY-2钻孔应变仪线差应变潮汐参数及其稳定性研究

介绍了泰安地震台YRY-2钻孔应变仪1991～1996年观测数据的调和分析结果．分析了潮汐参数的动态特征及其稳定性，并将有关结果与洞体水平线应变仪的（伸缩仪）观测结果进行了对比分析．泰安地震台YRY-2钻孔应变仪NS分量M2波月潮汐因子的离散中误差为3.3％，NE分量为3.6％，相位滞后的月离散误差小于2°．该指标与最好的洞室仪器SSY-Ⅱ的结果相当．     

青岛地震台钻孔体应变异常变化因素分析

分时段研究降雨、钻孔水位、工程施工等因素对青岛地震台体应变的影响，研究结果表明:钻孔水位反映区域地下水主要由降雨补给，降雨下渗改变地下水状态，并影响体应变观测；青岛体应变与钻孔水位的相关性及其周期特性均在2015年前后出现变化，可能与2015—2016年降雨偏少及工程施工有关；2018年1月17日台站钻孔施工很可能改变了体应变周围岩石孔隙环境，并扩大孔隙压力作用系数，可解释2018年3月以来水位小幅上升引起的体应变显著压性上升现象，受钻孔施工的影响，体应变与钻孔水位相关性的滞后特征明显减弱。